The present invention relates to an apparatus for forming and cutting thermoplastic sheets into formed sections.
The apparatus of the present invention is designed for use in the production of thermoplastic sheet products of various shapes and sizes. In recent years these thermoplastic products have found important applications, primarily in the packaging industry. The thermoplastic sheet is formed into the general shape of the product to be packaged, or into cup shape, and has a flange which is adhered to a cardboard backing. The type of package is sometimes called a "blister pack". The transparent quality of the thermoplastic material permits a display of the packaged product and increases its marketability and the package is convenient to handle and sell.
In the past machines have been proposed to form thermoplastic sheets into various shapes. In these machines the thermoplastic sheets are clamped between a heating platen, which softens the sheet, and a forming mold and a blade severs the formed sheet portion from its surrounding sheet. In one such machine a cutting blade is employed to partially penetrate the thermoplastic sheet to form a seal for a vacuum or for air pressure while the forming process is in progress. The vacuum or pressure forces the heat-softened sheet portion into the mold. At the conclusion of the forming process, the cutting blade is permitted to fully penetrate the thermoplastic sheet to sever the formed portion. In that machine there is a problem in cutting or in the sealing because the thermoplastic sheet is thin and a partial penetration of that thin sheet by the blade necessitates a high precision operation.